As there are six possibilities and we are considering the probability of the outcome NOT being a number 1, or being an odd number (that is, 1,3,5)- then there are 5 other possibilities and 3 other possibilities respectively.

wihch is to be expected since you have equal number of odd and even numbers on rhe cube. Third equallity is valid because events of getting number 1, number 3 and number 5 are mutually exclusive. For not mutally exclusive events A and B eg. `A = number geq 3` and `B = number leq 3` you would apply formula